This invention relates generally to the field of electronic devices. More specifically, it relates to a housing for a miniature electronic device, such as a potentiometer, wherein the housing includes means for mechanically retaining an electrical element therein without the need for thermal or adhesive bonding.
Many electronic devices, both miniature and subminiature, include a wirewound electrical element. Usually, the wirewound element functions as the resistive element in a potentiometric device. Typically, the wirewound element in a miniature potentiometer, for example, is secured to a seating surface enclosed within a housing. The element is retained in place on the seating surface by one of two methods. One method employs an epoxy preform placed on the surface and heat-cured to form an adhesive bond with the element. The other method requires the use of a thermoplastic composition for the seating surface, the thermoplastic being heat-softened to allow the element to sink partway into the seating surface. The heat required by both of these methods is usually applied by passing a relatively high electric current through the electrical element, a process sometimes referred to as "zapping" the element.
The above-described methods of retaining the element by either adhesive or thermal bonding add to the complexity of manufacturing the devices, and therefore, increase their cost. Also, the "zapping" of the element must be carefully controlled to avoid damage to the element.
To avoid the problems associated with thermal and adhesive bonding, purely mechanical retention means have been devised in various configurations. For example, wedging members have been employed, as shown in U.S. Pat. No. 2,476,294 to Hampton and U.S. Pat. No. 2,480,995 to Armitage. To date, however, such mechanical retention means have not been well-received for miniature devices, due to the relative difficulty of manufacturing the required mechanical structures on a physically-reduced scale.
Accordingly, it can be seen that there is a long-felt and yet unfilled need in the electronic device art for a purely mechanical means for element retention that is well-suited for miniaturization.